In vitro evaluation of VIP/PACAP receptors in healthy and diseased human tissues. Clinical implications

Ferroptosis in the Lacrimal Gland Is Involved in Dry Eye Syndrome Induced by Corneal Nerve Severing

Purpose

Dry eye syndrome (DES) is a prevalent postoperative complication after myopic corneal refractive surgeries and the main cause of postoperative dissatisfaction. Although great efforts have been made in recent decades, the molecular mechanism of postoperative DES remains poorly understood. Here, we used a series of bioinformatics approaches and experimental methods to investigate the potential mechanism involved in postoperative DES.

Methods

BALB/c mice were randomly divided into sham, unilateral corneal nerve cutting (UCNV) + saline, UCNV + vasoactive intestinal peptide (VIP), and UCNV + ferrostatin-1 (Fer-1, inhibitor of ferroptosis) groups. Corneal lissamine green dye and tear volume were measured before and two weeks after the surgery in all groups. Lacrimal glands were collected for secretory function testing, RNA sequencing, ferroptosis verification, and inflammatory factor detection.

Results

UCNV significantly induced bilateral decreases in tear secretion. Inhibition of the maturation and release of secretory vesicles was observed in bilateral lacrimal glands. More importantly, UCNV induced ferroptosis in bilateral lacrimal glands. Furthermore, UCNV significantly decreased VIP, a neural transmitter, in bilateral lacrimal glands, which increased Hif1a, the dominant transcription factor of transferrin receptor protein 1 (TfR1). Supplementary VIP inhibited ferroptosis, which decreased the inflammatory reaction and promoted the maturation and release of secretory vesicles. Supplementary VIP and Fer-1 improved tear secretion.

Conclusions

Our data suggest a novel mechanism by which UCNV induces bilateral ferroptosis through the VIP/Hif1a/TfR1 pathway, which might be a promising therapeutic target for DES-induced by corneal refractive surgeries.

Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors

Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.

A distinctive ligand recognition mechanism by the human vasoactive intestinal polypeptide receptor 2

Class B1 of G protein-coupled receptors (GPCRs) comprises 15 members activated by physiologically important peptide hormones. Among them, vasoactive intestinal polypeptide receptor 2 (VIP2R) is expressed in the central and peripheral nervous systems and involved in a number of pathophysiological conditions, including pulmonary arterial hypertension, autoimmune and psychiatric disorders, in which it is thus a valuable drug target. Here, we report the cryo-electron microscopy structure of the human VIP2R bound to its endogenous ligand PACAP27 and the stimulatory G protein. Different from all reported peptide-bound class B1 GPCR structures, the N-terminal α-helix of VIP2R adopts a unique conformation that deeply inserts into a cleft between PACAP27 and the extracellular loop 1, thereby stabilizing the peptide-receptor interface. Its truncation or extension significantly decreased VIP2R-mediated cAMP accumulation. Our results provide additional information on peptide recognition and receptor activation among class B1 GPCRs and may facilitate the design of better therapeutics.

Vasoactive intestinal polypeptide receptor 2 (VIP2R) is involved in immunity. Here, the authors report two cryo-EM structures of the VIP2R–G_s in complex with the endogenous peptide ligand PACAP27, revealing a unique interaction mode between PACAP27 and the receptor, stabilized by the N-terminal α-helix of VIP2R.

A photosensitizing fusion protein with targeting capabilities

The photodynamic treatment for antimicrobial applications or anticancer therapy relies on reactive oxygen species generated by photosensitizing molecules after absorption of visible or near-infrared light. If the photosensitizing molecule is in close vicinity of the microorganism or the malignant cell, a photocytotoxic action is exerted. Therefore, the effectiveness of photosensitizing compounds strongly depends on their capability to target microbial or cancer-specific proteins. In this study, we report on the preparation and preliminary characterization of human recombinant myoglobin fused to the vasoactive intestinal peptide to target vasoactive intestinal peptide receptor (VPAC) receptors. Fe-protoporphyrin IX was replaced by the photosensitizing compound Zn-protoporphyrin IX. Taking advantage of the fluorescence emission by Zn-protoporphyrin IX, we show that the construct can bind prostate cancer cells where the VPAC receptors are expressed.

The VIP/VPAC1R Pathway Regulates Energy and Glucose Homeostasis by Modulating GLP-1, Glucagon, Leptin and PYY Levels in Mice

Simple Summary

The current study is the first complete characterization of the phenotypic, metabolic, calorimetric, and homeostatic effects of VPAC1R in a null murine model. To evaluate the role of VPAC1R on body phenotype, feeding behavior, glucose/energy homeostasis, metabolic rate and plasma hormones, a long-term study was conducted in VPAC1R^−/− and WT mice. The outcome data document that VPAC1R^−/− mice have altered metabolism and insulin intolerance, with significant increase of feeding bouts, reduction of total energy expenditure and respiratory gases during both the dark and light cycle, together with elevated fasting levels of GLP-1 and PYY, and higher postprandial levels of GLP-1, glucagon leptin and PYY. These findings suggests that VPAC1R controls glucose homeostasis and energy balance by regulating plasma metabolic hormones.

Abstract

Vasoactive Intestinal Peptide binds with high affinity to VPAC1R and VPAC2R, thus regulating key physiologic functions. Previously, we documented in VIP^−/− mice a leaner body phenotype and altered metabolic hormones. Past reports described in VPAC2^−/− mice impaired circadian rhythm, reduced food intake, and altered metabolism. To better define the effects of VPAC1R on body phenotype, energy/glucose homeostasis, and metabolism, we conducted a 12-week study in a VPAC1R null model. Our results reveal that VPAC1^−/− mice experienced significant metabolic alterations during the dark cycle with greater numbers of feeding bouts (p = 0.009), lower Total Energy Expenditure (p = 0.025), VO₂ (p = 0.029), and VCO₂ (p = 0.016); as well as during the light cycle with lower Total Energy Expenditure (p = 0.04), VO₂ (p = 0.044), and VCO₂ (p = 0.029). Furthermore, VPAC1^−/− mice had significantly higher levels of GLP-1 and PYY during fasting, and higher levels of GLP-1, glucagon leptin and PYY during postprandial conditions. In addition, VPAC1^−/− mice had lower levels of glucose at 60′ and 120′, as assessed by insulin tolerance test. In conclusion, this study supports a key role for VPAC1R in the regulation of body glucose/energy homeostasis and metabolism.

Therapeutic potential of vasoactive intestinal peptide and its receptor VPAC2 in type 2 diabetes

Owing to the increasing prevalence of type 2 diabetes, the development of novel hypoglycemic drugs has become a research hotspot, with the ultimate goal of developing therapeutic drugs that stimulate glucose-induced insulin secretion without inducing hypoglycemia. Vasoactive intestinal peptide (VIP), a 28-amino-acid peptide, can stimulate glucose-dependent insulin secretion, particularly by binding to VPAC2 receptors. VIP also promotes islet β-cell proliferation through the forkhead box M1 pathway, but the specific molecular mechanism remains to be studied. The clinical application of VIP is limited because of its short half-life and wide distribution in the human body. Based on the binding properties of VIP and VPAC2 receptors, VPAC2-selective agonists have been developed to serve as novel hypoglycemic drugs. This review summarizes the physiological significance of VIP in glucose homeostasis and the potential therapeutic value of VPAC2-selective agonists in type 2 diabetes.

Molecular Imaging in Primary Staging of Prostate Cancer Patients: Current Aspects and Future Trends

Accurate primary staging is the cornerstone in all malignancies. Different morphological imaging modalities are employed in the evaluation of prostate cancer (PCa). Regardless of all developments in imaging, invasive histopathologic evaluation is still the standard method for the detection and staging of the primary PCa. Magnetic resonance imaging (MRI) and computed tomography (CT) play crucial roles; however, functional imaging provides additional valuable information, and it is gaining ever-growing acceptance in the management of PCa. Targeted imaging with different radiotracers has remarkably evolved in the past two decades. [111In]In-capromab pendetide scintigraphy was a new approach in the management of PCa. Afterwards, positron emission tomography (PET) tracers such as [11C/18F]choline and [11C]acetate were developed. Nevertheless, none found a role in the primary staging. By introduction of the highly sensitive small molecule prostate-specific membrane antigen (PSMA) PET/CT, as well as recent developments in MRI and hybrid PET/MRI systems, non-invasive staging of PCa is being contemplated. Several studies investigated the role of these sophisticated modalities in the primary staging of PCa, showing promising results. Here, we recapitulate the role of targeted functional imaging. We briefly mention the most popular radiotracers, their diagnostic accuracy in the primary staging of PCa, and impact on patient management.

Resequencing and SNP discovery of Amur ide (Leuciscus waleckii) provides insights into local adaptations to extreme environments

Amur ide (Leuciscus waleckii), a Cyprinid species, is broadly distributed in Northeast Asia. Different from its freshwater counterparts, the population in Lake Dali Nor has a strong alkalinity tolerance and can adapt to extremely alkali-saline water with bicarbonate over 50 mmol/L. To uncover the genetic basis of its alkaline adaptation, three populations, including one alkali form from Lake Dali Nor (DL), one freshwater form from its adjacent sister Lake Ganggeng Nor (GG), and one freshwater form from its historical origin, namely, the Songhua River (SH), were analyzed using genome resequencing technology. A total of 679.82 Gb clean data and 38,091,163 high-quality single-nucleotide polymorphism (SNP) loci were detected in the three populations. Nucleotide diversity and population structure analysis revealed that the DL and GG populations have lower nucleotide diversities and different genetic structures than those of the SH population. Selective sweeping showed 21 genes involved in osmoregulatory regulation (DLG1, VIPR1, AKT1, and GNAI1), inflammation and immune responses (DLG1, BRINP1, CTSL, TRAF6, AKT1, STAT3, GNAI1, SEC22b, and PSME4b), and cardiorespiratory development (TRAF6, PSME4b, STAT3, AKT1, and COL9A1) to be associated with alkaline adaption of the DL population. Interestingly, selective pressure (CodeML, MEME, and FEL) methods identified two functional codon sites of VIPR1 to be under positive selection in the DL population. The subsequent 3D protein modeling confirmed that these selected sites will incur changes in protein structure and function in the DL population. In brief, this study provides molecular evidence of population divergence and alkaline adaptation, which will be very useful for revealing the genetic basis of alkaline adaptation in Amur ide.

Targeting VPAC1 Receptors for Imaging Glioblastoma

PURPOSE

Scintigraphic imaging of malignant glioblastoma (MG) continues to be challenging. We hypothesized that VPAC1 cell surface receptors can be targeted for positron emission tomography (PET) imaging of orthotopically implanted MG in a mouse model, using a VPAC1-specific peptide [⁶⁴Cu]TP3805.

PROCEDURES

The expression of VPAC1 in mouse GL261 and human U87 glioma cell lines was determined by western blot. The ability of [⁶⁴Cu]TP3805 to bind to GL261 and U87 cells was studied by cell-binding. Receptor-blocking studies were performed to validate receptor specificity. GL261 tumors were implanted orthotopically in syngeneic T-bet knockout C57BL/6 mouse brain (N = 15) and allowed to grow for 2-3 weeks. Mice were injected i.v., first with ~ 150 μCi of 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) then 24 h later with ~ 200 μCi of [⁶⁴Cu]TP3805. In another set of tumor-bearing mice, (N = 5), ionic [⁶⁴Cu]Cl₂ was injected as a control. Mice were imaged at a 2-h post-injection using an Inveon micro-PET/CT, sacrificed and % ID/g of [⁶⁴Cu]TP3805 and [⁶⁴Cu]Cl₂ were calculated in a tumor, normal brain, and other tissues. For histologic tissue examination, 3-μm thick sections of the tumors and normal brain were prepared, digital autoradiography (DAR) was performed, and then the sections were H&E stained for histologic examination.

RESULTS

Western blots showed a strong signal for VPAC1 on both cell lines. [⁶⁴Cu]TP3805 cell-binding was 87 ± 1.5 %. Receptor-blocking reduced cell-binding to 24.3 ± 1.5 % (P < 0.01). PET imaging revealed remarkable accumulation of [⁶⁴Cu]TP3805 in GL261 MG with a negligible background in the normal brain, as compared to [¹⁸F]FDG. Micro-PET/CT image analyses and tissue distribution showed that the brain tumor uptake for [⁶⁴Cu]TP3805 was 8.2 ± 1.7 % ID/g and for [⁶⁴Cu]Cl₂ 2.1 ± 0.5 % ID/g as compared to 1.0 ± 0.3 % ID/g and 1.4 ± 0.3 % ID/g for normal mouse brains, respectively. The high tumor/normal brain ratio for [⁶⁴Cu]TP3805 (8.1 ± 1.1) allowed tumors to be visualized unequivocally. Histology and [⁶⁴Cu]TP3805 DAR differentiated malignant tumors from healthy brain and confirmed PET findings.

CONCLUSION

Targeting VPAC1 receptors using [⁶⁴Cu]TP3805 for PET imaging of MG is a promising novel approach and calls for further investigation.

Cryo-EM structure of an activated VIP1 receptor-G protein complex revealed by a NanoBiT tethering strategy

Vasoactive intestinal polypeptide receptor (VIP1R) is a widely expressed class B G protein-coupled receptor and a drug target for the treatment of neuronal, metabolic, and inflammatory diseases. However, our understanding of its mechanism of action and the potential of drug discovery targeting this receptor is limited by the lack of structural information of VIP1R. Here we report a cryo-electron microscopy structure of human VIP1R bound to PACAP27 and Gs heterotrimer, whose complex assembly is stabilized by a NanoBiT tethering strategy. Comparison with other class B GPCR structures reveals that PACAP27 engages VIP1R with its N-terminus inserting into the ligand binding pocket at the transmembrane bundle of the receptor, which subsequently couples to the G protein in a receptor-specific manner. This structure has provided insights into the molecular basis of PACAP27 binding and VIP receptor activation. The methodology of the NanoBiT tethering may help to provide structural information of unstable complexes.

Vasoactive intestinal polypeptide receptor (VIP1R) is a widely expressed class B G protein-coupled receptor and a drug target for the treatment of inflammatory diseases. Here authors report a cryoelectron microscopy structure of human VIP1R bound to PACAP27 and Gs heterotrimer, which provides insights into PACAP27 binding and VIP receptor activation.

Recent advances in vasoactive intestinal peptide physiology and pathophysiology: focus on the gastrointestinal system

Vasoactive intestinal peptide (VIP), a gut peptide hormone originally reported as a vasodilator in 1970, has multiple physiological and pathological effects on development, growth, and the control of neuronal, epithelial, and endocrine cell functions that in turn regulate ion secretion, nutrient absorption, gut motility, glycemic control, carcinogenesis, immune responses, and circadian rhythms. Genetic ablation of this peptide and its receptors in mice also provides new insights into the contribution of VIP towards physiological signaling and the pathogenesis of related diseases. Here, we discuss the impact of VIP on gastrointestinal function and diseases based on recent findings, also providing insight into its possible therapeutic application to diabetes, autoimmune diseases and cancer.

Identification of hepatitis B virus and liver cancer bridge molecules based on functional module network

BACKGROUND

The potential role of chronic inflammation in the development of cancer has been widely recognized. However, there has been little research fully and thoroughly exploring the molecular link between hepatitis B virus (HBV) and hepatocellular carcinoma (HCC).

AIM

To elucidate the molecular links between HBV and HCC through analyzing the molecular processes of HBV-HCC using a multidimensional approach.

METHODS

First, maladjusted genes shared between HBV and HCC were identified by disease-related differentially expressed genes. Second, the protein-protein interaction network based on dysfunctional genes identified a series of dysfunctional modules and significant crosstalk between modules based on the hypergeometric test. In addition, key regulators were detected by pivot analysis. Finally, targeted drugs that have regulatory effects on diseases were predicted by modular methods and drug target information.

RESULTS

The study found that 67 genes continued to increase in the HBV-HCC process. Moreover, 366 overlapping genes in the module network participated in multiple functional blocks. It could be presumed that these genes and their interactions play an important role in the relationship between inflammation and cancer. Correspondingly, significant crosstalk constructed a module level bridge for HBV-HCC molecular processes. On the other hand, a series of non-coding RNAs and transcription factors that have potential pivot regulatory effects on HBV and HCC were identified. Among them, some of the regulators also had persistent disorders in the process of HBV-HCC including microRNA-192, microRNA-215, and microRNA-874, and early growth response 2, FOS, and Kruppel-like factor 4. Therefore, the study concluded that these pivots are the key bridge molecules outside the module. Last but not least, a variety of drugs that may have some potential pharmacological or toxic side effects on HBV-induced HCC were predicted, but their mechanisms still need to be further explored.

CONCLUSION

The results suggest that the persistent inflammatory environment of HBV can be utilized as an important risk factor to induce the occurrence of HCC, which is supported by molecular evidence.

VIP Regulates Morphology and F-Actin Distribution of Schlemm's Canal in a Chronic Intraocular Pressure Hypertension Model via the VPAC2 Receptor

Purpose

To investigate the roles of vasoactive intestinal peptides (VIPs) in regulating the morphology and F-actin distribution of Schlemm's canal (SC) of rat eyes.

Methods

Chronic intraocular pressure (IOP) hypertension models with episcleral venous cauterization (EVC) were treated with topical VIP or PG99-465 (vasoactive intestinal peptide receptors 2 [VPAC2] antagonist). IOPs were measured with Tono-Pen, and the SC parameters, including the cross-section area, circumference, and length, were statistically evaluated by hematoxylin-eosin and CD31 immunohistochemical staining. Immunofluorescence was performed to detect the distribution of F-actin in the SC. Moreover, the distribution of filamentous actin (F-actin) and globular actin (G-actin) in human umbilical vein endothelial cells (HUVECs) was studied under a pressure system by immunofluorescence and Western blotting.

Results

Increased expressions of VIP and VPAC2 receptors, as well as a disordered distribution of F-actin were found in SC endothelial cells (SCEs) in the EVC model. Moreover, topical VIP maintained the normal distribution of F-actin in SCEs, expanded the collapsed SC, and induced a significant decrease in IOP in the EVC model. In in vitro HUVECs, the F-actin/G-actin ratio increased significantly under stress stimulation for 30 minutes. A total of 50 μM VIP helped maintain the normal F-actin/G-actin ratio of HUVECs against stress stimulation.

Conclusions

VIP regulates the distribution of F-actin in SCEs via the VPAC2 receptor in order to induce a decrease in IOP. VIP may represent a new target for antiglaucoma drugs.

Signaling pathways activated by PACAP in MCF-7 breast cancer cells

PACAP has opposing roles ranging from activation to inhibition of tumor growth and PACAP agonists/antagonists could be used in tumor therapy. In this study, the effect of PACAP stimulation on signaling pathways was investigated in MCF-7 human adenocarcinoma breast cancer cells. Results showed that MCF-7 cells express VPAC1 and VPAC2, but not PAC1, receptors. In addition, PACAP increased the phosphorylation levels of STAT1, Src and Raf within seconds, confirming their involvement in early stages of PACAP signaling whereas maximal phosphorylation of AKT, ERK and p38 was reached 10 to 20 min later. Moreover, selective inhibition of Src or PI3K resulted in a significant decrease in the phosphorylation of ERK and AKT, but not p38, demonstrating that PACAP signaling follows Src/Raf/ERK and PI3K/AKT pathways. On the other hand, selective inhibition of PLC or PKA resulted in a significant decrease in the phosphorylation of p38, but not AKT or ERK, indicating that PACAP signaling also follows the PLC and PKA/cAMP pathways. Furthermore, PACAP induced ROS through H₂O₂ production whereas pretreatment with NAC inhibitor decreased AKT and ERK phosphorylation, but not p38. Selective NOX2 inhibition affected Src/Raf/Erk and PI3K/Akt pathways, without affecting the p38/PLC/PKA pathway whereas other inhibitors (ML171, VAS2870) had no effect on PACAP induced ROS generation. On the other hand, PACAP induced calcium release, which was decreased by pretreatment with PLC inhibitor. Finally, PACAP stimulation promoted apoptosis by increasing Bax and decreasing Bcl2 expression. In conclusion, we demonstrated that PACAP signaling in MCF-7 cells follows the Src/Raf/ERK and PI3K/AKT pathways and is VPAC1 dependent in a ROS dependent manner, whereas it follows PLC and PKA/cAMP pathways and is VPAC2 dependent through p38 MAP kinase activation involving calcium.

VPAC1-targeted PET/CT scan: improved molecular imaging for the diagnosis of prostate cancer using a novel cell surface antigen

PURPOSE

Current approaches to prostate cancer screening and diagnosis are plagued with limitations in diagnostic accuracy. There is a compelling need for biomolecular imaging that will not only detect prostate cancer early but also distinguish prostate cancer from benign lesions accurately. In this topic paper, we review evidence that supports further investigation of VPAC1-targeted PET/CT imaging in the primary diagnosis of prostate cancer.

METHODS

A non-systematic review of Medline/PubMed was performed. English language guidelines on prostate cancer diagnosis and management, original articles, and review articles were selected based on their clinical relevance.

RESULTS

VPAC1 receptors were overexpressed 1000 times more in prostate cancer than benign prostatic stromal tissue. In vitro and in vivo studies showed that Copper-64 labeled analogs of VPAC1 ligands can be synthesized with high radiochemical efficiency and purity. The radioactive probes had excellent VPAC1 receptor binding specificity and affinity. They had good biochemical stability in vitro and in mouse and human serum. They had minimal urinary excretion, which made them favorable for prostate cancer imaging. Initial feasibility study in men with prostate cancer showed that the probes were safe with no reported adverse reaction. 64Cu-TP3805 PET/CT detected 98% of prostate cancer lesions and nodal metastasis as confirmed with whole mount histopathological evaluation.

CONCLUSIONS

VPAC1 receptors are promising targets for biomolecular imaging of primary prostate cancer that can distinguish malignant from benign lesions non-invasively. Further investigations are warranted to validate initial findings and define the clinical utilities of VPAC1-targeted PET imaging for prostate cancer diagnosis and management.

Presence and Effects of Pituitary Adenylate Cyclase Activating Polypeptide Under Physiological and Pathological Conditions in the Stomach

Pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide with widespread occurrence throughout the body including the gastrointestinal system. In the small and large intestine, effects of PACAP on cell proliferation, secretion, motility, gut immunology and blood flow, as well as its importance in bowel inflammatory reactions and cancer development have been shown and reviewed earlier. However, no current review is available on the actions of PACAP in the stomach in spite of numerous data published on the gastric presence and actions of the peptide. Therefore, the aim of the present review is to summarize currently available data on the distribution and effects of PACAP in the stomach. We review data on the localization of PACAP and its receptors in the stomach wall of various mammalian and non-mammalian species, we then give an overview on PACAP's effects on secretion of gastric acid and various hormones. Effects on cell proliferation, differentiation, blood flow and gastric motility are also reviewed. Finally, we outline PACAP's involvement and changes in various human pathological conditions.

Neuropeptide Levels as well as Neprilysin Activity Decrease in Renal Cell Carcinoma

Calcitonin Gene-related Peptide (CGRP), Vasoactive Intestinal Peptide (VIP) and Substance P (SP) are sensory neuropeptides which may alter cancer growth through modulation of chronic inflammation. We recently reported that SP suppresses breast cancer growth and metastasis through neuroimmune modulation. These neuropeptides are hydrolyzed by Neprilysin (NEP) to bioactive fragments. Decreased activity of NEP was reported in clear cell and chromophobe type renal cell carcinoma (RCC). It is however not known how the levels of neuropeptides hydrolyzed with NEP changes in RCC. Decrease activity of SP and CGRP containing sensory nerve endings was previously reported to increase cancer metastasis in animal models. It is however not known how peptidergic nerve endings are altered in RCC. Hence we here evaluated the levels of neuronal and non-neuronal neuropeptides and NEP activity in RCC including papillary type as well as neighboring uninvolved kidney. A cross-sectional study was conducted in 57 patients undergoing radical nephrectomy and diagnosed with RCC. NEP activity, levels and expression were determined using flourogenic substrate, western blot and qPCR respectively in freshly-frozen tissues. Immunohistochemical analyses were also performed. Neuronal and non-neuronal levels of CGRP, SP and VIP levels were determined using two-step acetic acid extraction. Levels and activity of NEP were markedly decreased in RCC regardless of subtype. Similar levels of VIP were detected in first and second extractions. VIP levels were higher in clear cell and papillary RCC compared to nearby kidney tissue. VIP levels of neighboring kidney tissue of papillary type RCC was significantly lower compared to kidney samples from clear cell RCC. CGRP levels were higher in second extraction. Similar to VIP levels, CGRP levels of neighboring kidney tissue from clear cell and chromophobe type RCC was significantly lower compared to corresponding tumor samples, an effect observed in the second extraction. VIP and CGRP levels of nearby kidney tissue varied subtype dependently demonstrating that different subtypes of RCC alter their local environment differently. Furthermore NEP-induce hydrolysis of VIP creates selective VPAC-1 receptor agonist which has anti-proliferative and anti-inflammatory effects. Hence loss of NEP activity may prevent anti-tumoral effects of VIP on RCC.

Distribution and Function of PACAP and Its Receptors in the Healthy and Nephrotic Kidney

BACKGROUND/AIMS

Plasma deficiency of pituitary adenylate cyclase-activating polypeptide (PACAP) was recently demonstrated in children with nephrotic syndrome (NS). Previous studies have reported an important protective effect of PACAP on kidney proximal tubules. The aim of this study was to explore the expression of PACAP and its receptors PAC1, VPAC1 and VPAC2 in the healthy and nephrotic kidney and to determine if PACAP has an effect on renal proximal tubular cells exposed to albumin.

METHODS

Expression of PACAP and its receptors was studied using kidney tissue from healthy and nephrotic children, and in 3 human renal cell lines (glomerular microvascular endothelial cells, podocytes and proximal tubular epithelial HK-2 cells). The functionality of the VPAC1 receptor was tested in HK-2 cells, measuring cyclic adenosine monophosphate levels after PACAP exposure. The influence of PACAP on cell viability and transforming growth factor-β1 (TGF-β1) expression was measured in HK-2 cells exposed to albumin, mimicking proteinuria related damage.

RESULTS

VPAC1 expression was detected in the tubular proximal epithelial cells and in the glomerular podocytes of renal tissue from healthy and nephrotic children. Increased staining for PACAP was found in the proximal tubules of renal sections from children with NS compared to healthy renal sections. Expression and functionality of VPAC1 were demonstrated in HK-2 cells. Finally, PACAP did not alter cell viability or TGF-β1 expression of HK-2 cells exposed to albumin.

CONCLUSION

VPAC1 is the predominant receptor in the human kidney. The enhanced presence of PACAP in proximal tubular epithelial cells in nephrotic kidneys points to the reabsorption of filtered PACAP. On short term, PACAP has no in vitro effect on cell viability and TGF-β1 expression of proximal tubular epithelial cells exposed to high concentrations of albumin.

VIP-targeted Cytotoxic Nanomedicine for Breast Cancer

Cancer chemotherapy is hampered by serious toxicity to healthy tissues. Conceivably, encapsulation of cytotoxic drugs in actively-targeted, biocompatible nanocarriers could overcome this problem. Accordingly, we used sterically stabilized mixed micelles (SSMM) composed of biocompatible and biodegradable phospholipids to solubilize paclitaxel (P), a hydrophobic model cytotoxic drug, and deliver it to breast cancer in rats. To achieve active targeting, the surface of SSMM was grafted with a ligand, human vasoactive intestinal peptide (VIP) that selectively interacts with its cognate receptors overexpressed on breast cancer cells. We found that even in vitro cytotoxicity of P-SSMM-VIP was 2-fold higher that that of free paclitaxel (p<0.05). Given the unique attributes of P-SSMM and P-SSMM-VIP, most notable small hydrodynamic diameter (~15nm) and stealth properties, biodistribution of paclitaxel was significantly altered. Accumulation of paclitaxel in breast tumor was highest for P-SSMM-VIP, followed by P-SSMM and Cremophor based paclitaxel (PTX). Importantly, bone marrow accumulation of paclitaxel encapsulated in both SSMM-VIP and SSMM was significantly less than that of PTX. Administration of clinically-relevant dose of paclitaxel (5mg/kg) as P-SSMM-VIP and P-SSMM eradicated carcinogen-induced orthotopic breast cancer in rats, whereas PTX decreased tumor size by only 45%. In addition, a 5-fold lower dose (1mg/kg) of paclitaxel in actively targeted P-SSMM-VIP was associated with ~80% reduction in tumor size while the response to PTX and P-SSMM was significantly less. Hypotension was not observed when VIP was grafted onto SSMM. Based on our findings, we propose further development of effective and safe VIP-grafted phospholipid micelle nanomedicines of anti-cancer drugs for targeted treatment of solid tumors in humans.

Pituitary adenylate cyclase-activating polypeptide protects glomerular podocytes from inflammatory injuries

Diabetic nephropathy (DN) is a leading cause of end-stage kidney disease; however, there are few treatment options. Inflammation plays a crucial role in the initiation and/or progression of DN. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide, which was originally isolated from the ovine hypothalamus and reportedly has diverse biological functions. It has been reported that PACAP has renoprotective effects in different models of kidney pathology. However, the specific cell types within the kidney that are protected by PACAP have not yet been reported. In this study, we localized VPAC1, one of the PACAP receptors, to glomerular podocytes, which also reportedly has crucial roles not only in glomerular physiology but also in pathology. PACAP was effective in the downregulation of proinflammatory cytokines, such as monocyte chemoattractant protein-1 (MCP-1) and interleukin-6, which had been induced by the activation of toll-like receptor (TLR) with lipopolysaccharide. PACAP also had downregulated the expression of MCP-1 through the protein kinase A signaling pathway; this led to the attenuation of the activation of extracellular signal-regulated kinase and nuclear factor-kappa B signaling. Our results suggested that PACAP could be a possible treatment option for DN through the use of anti-inflammation effects on glomerular podocytes.

The effects of pituitary adenylate cyclase activating polypeptide in renal ischemia/reperfusion

Pituitary adenylate cyclase activating polypeptide (PACAP ) is a multifunctional neuropeptide occurring in the nervous system as well as in the peripheral organs. Beneficial action of PACAP has been shown in different pathological processes. The strong protective effects of the peptide are probably due to its complex modulatory actions in antiapoptotic, anti-inflammatory and antioxidant pathways. In the kidney, PACAP is protective in models of diabetic nephropathy, myeloma kidney injury, cisplatin-, gentamycin- and cyclosporin-induced damages. Numerous studies have been published describing the protective effect of this peptide in renal ischemia/reperfusion. The present review focuses on the ischemia/reperfusion-induced kidney injury and gives a brief summary about the results published in this area.

VPAC2 receptor agonist BAY 55-9837 increases SMN protein levels and moderates disease phenotype in severe spinal muscular atrophy mouse models

Background

Spinal Muscular Atrophy (SMA) is one of the most common inherited causes of infant death and is caused by the loss of functional survival motor neuron (SMN) protein due to mutations or deletion in the SMN1 gene. One of the treatment strategies for SMA is to induce the expression of the protein from the homologous SMN2 gene, a rescuing paralog for SMA.

Methods and results

Here we demonstrate the promise of pharmacological modulation of SMN2 gene by BAY 55-9837, an agonist of the vasoactive intestinal peptide receptor 2 (VPAC2), a member of G protein coupled receptor family. Treatment with BAY 55-9837 lead to induction of SMN protein levels via activation of MAPK14 or p38 pathway in vitro. Importantly, BAY 55-9837 also ameliorated disease phenotype in severe SMA mouse models.

Conclusion

Our findings suggest the VPAC2 pathway is a potential SMA therapeutic target.

Mechanisms involved in VPAC receptors activation and regulation: lessons from pharmacological and mutagenesis studies

Vasoactive intestinal peptide (VIP) plays diverse and important role in human physiology and physiopathology and their receptors constitute potential targets for the treatment of several diseases such as neurodegenerative disorder, asthma, diabetes, and inflammatory diseases. This article reviews the current knowledge regarding the two VIP receptors, VPAC(1) and VPAC(2), with respect to mechanisms involved in receptor activation, G protein coupling, signaling, regulation, and oligomerization.

Early changes in pituitary adenylate cyclase-activating peptide, vasoactive intestinal peptide and related receptors expression in retina of streptozotocin-induced diabetic rats

The retinal expression and distribution of pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) and their receptors was investigated in early streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in rats by STZ injection (60 mg/kg i.p.). PACAP, VIP and their receptors in nondiabetic control and diabetic retinas were assayed by quantitative real-time PCR and Western blot 1 and 3 weeks after STZ injection. Effects of intravitreal treatment with PACAP38 on the expression of the two apoptotic-related genes Bcl-2 and p53 were also evaluated. PACAP and VIP, as well as VPAC1 and VPAC2 receptors, but not PAC1 mRNA levels, were transiently induced in retinas 1 week following STZ. These findings were confirmed by immunoblot analyses. Three weeks after the induction of diabetes, significant decreases in the expression of peptides and their receptors were observed, Bcl-2 expression decreased and p53 expression increased. Intravitreal injection of PACAP38 restored STZ-induced changes in retinal Bcl-2 and p53 expression to nondiabetic levels. The initial upregulation of PACAP, VIP and related receptors and the subsequent downregulation in retina of diabetic rats along with the protective effects of PACAP38 treatment, suggest a role for both peptides in the pathogenesis of diabetic retinopathy.

Pharmacology and functions of receptors for vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide: IUPHAR review 1

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are members of a superfamily of structurally related peptide hormones that includes glucagon, glucagon-like peptides, secretin, gastric inhibitory peptide (GIP) and growth hormone-releasing hormone (GHRH). VIP and PACAP exert their actions through three GPCRs - PAC(1) , VPAC(1) and VPAC(2) - belonging to class B (also referred to as class II, or secretin receptor-like GPCRs). This family comprises receptors for all peptides structurally related to VIP and PACAP, and also receptors for parathyroid hormone, corticotropin-releasing factor, calcitonin and related peptides. PAC(1) receptors are selective for PACAP, whereas VPAC(1) and VPAC(2) respond to both VIP and PACAP with high affinity. VIP and PACAP play diverse and important roles in the CNS, with functions in the control of circadian rhythms, learning and memory, anxiety and responses to stress and brain injury. Recent genetic studies also implicate the VPAC(2) receptor in susceptibility to schizophrenia and the PAC(1) receptor in post-traumatic stress disorder. In the periphery, VIP and PACAP play important roles in the control of immunity and inflammation, the control of pancreatic insulin secretion, the release of catecholamines from the adrenal medulla and as co-transmitters in autonomic and sensory neurons. This article, written by members of the International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification (NC-IUPHAR) subcommittee on receptors for VIP and PACAP, confirms the existing nomenclature for these receptors and reviews our current understanding of their structure, pharmacology and functions and their likely physiological roles in health and disease. More detailed information has been incorporated into newly revised pages in the IUPHAR database (http://www.iuphar-db.org/DATABASE/FamilyMenuForward?familyId=67).

Remote control of renal physiology by the intestinal neuropeptide pigment-dispersing factor in Drosophila

The role of the central neuropeptide pigment-dispersing factor (PDF) in circadian timekeeping in Drosophila is remarkably similar to that of vasoactive intestinal peptide (VIP) in mammals. Like VIP, PDF is expressed outside the circadian network by neurons innervating the gut, but the function and mode of action of this PDF have not been characterized. Here we investigate the visceral roles of PDF by adapting cellular and physiological methods to the study of visceral responses to PDF signaling in wild-type and mutant genetic backgrounds. We find that intestinal PDF acts at a distance on the renal system, where it regulates ureter contractions. We show that PdfR, PDF's established receptor, is expressed by the muscles of the excretory system, and present evidence that PdfR-induced cAMP increases underlie the myotropic effects of PDF. These findings extend the similarities between PDF and VIP beyond their shared central role as circadian regulators, and uncover an unexpected endocrine mode of myotropic action for an intestinal neuropeptide on the renal system.

Progress in understanding the role of vasoactive intestinal polypeptide in the pathogenesis of digestive diseases

Vasoactive intestinal polypeptide (VIP) is not only a gastrointestinal hormone but also a neuropeptide. It is an important brain-gut peptide that relates to many disciplines such as physiology, biochemistry, cell biology, molecular biology, neurology, and immunology. It is distributed in the liver, biliary tract, pancreas, and gastrointestinal tract, and has close relationship with digestive diseases. In pathological states, VIP was degraded slowly. Once its content and receptor sensitivity change, multiple diseases, especially secretory function disorders of the digestive system, may be caused. This article summarizes the characteristics and functions of VIP as well as its relationship with the pathogenesis of digestive diseases.

PACAP immunoreactivity in human malignant tumor samples and cardiac diseases

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide having important roles in various physiological processes. Recent trends in PACAP research point to the clinical introduction of PACAP or its analogs/fragments possibly in the near future. Recently, we have shown the presence of PACAP in human plasma, milk, placenta, and follicular fluid samples. However, relatively few data are available on PACAP in human tissues from patients with different disorders. The aim of the present study was to determine, by radioimmunoassay, the tissue level of PACAP38-like immunoreactivity (LI) and PACAP27-LI in different primary non-small cell lung cancer, colon tumor samples, and in cardiac muscle samples from patients suffering from ischemic heart disease and valvular disorders. We also labeled the PAC1 receptors in human cardiac cells. All samples showed significantly higher PACAP38-LI compared with PACAP27-LI. We found significantly lower levels of PACAP38-LI and PACAP27-LI in tumoral and peripheral samples compared with normal healthy tissue in both lung and colon cancers. Further investigations are necessary to describe the exact function of PACAP in oncogenesis. We showed that PACAP38-LI and PACAP27-LI are significantly higher in ischemic heart diseases compared with valvular abnormalities, suggesting that PACAP might play a role in ischemic heart disorders.

Effects of pituitary adenylate cyclase activating polypeptide in the urinary system, with special emphasis on its protective effects in the kidney

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widespread neuropeptide with diverse effects in the nervous system and peripheral organs. One of the most well-studied effects of PACAP is its cytoprotective action, against different harmful stimuli in a wide variety of cells and tissues. PACAP occurs in the urinary system, from the kidney to the lower urinary tract. The present review focuses on the nephroprotective effects of PACAP and summarizes data obtained regarding the protective effects of PACAP in different models of kidney pathologies. In vitro data show that PACAP protects tubular cells against oxidative stress, myeloma light chain, cisplatin, cyclosporine-A and hypoxia. In vivo data provide evidence for its protective effects in ischemia/reperfusion, cisplatin, cyclosporine-A, myeloma kidney injury, diabetic nephropathy and gentamicin-induced kidney damage. Results accumulated on the renoprotective effects of PACAP suggest that PACAP is an emerging candidate for treatment of human kidney pathologies.

Vasoactive intestinal peptide reduces oxidative stress in pancreatic acinar cells through the inhibition of NADPH oxidase

Vasoactive intestinal peptide (VIP) attenuates experimental acute pancreatitis (AP) by inhibition of cytokine production from inflammatory cells. It has been suggested that reactive oxygen species (ROS) as well as cytokines play pivotal roles in the early pathophysiology of AP. This study aimed to clarify the effect of VIP on the oxidative condition in pancreas, especially pancreatic acinar cells (acini). Hydrogen peroxide (H(2)O(2))-induced intracellular ROS, assessed with CM-H(2)DCFDA, increased time- and dose-dependently in acini isolated from rats. Cell viability due to ROS-induced cellular damage, evaluated by MTS assay, was decreased with ≥100 μmol/L H(2)O(2). VIP significantly inhibited ROS production from acini and increased cell viability in a dose-dependent manner. Expression of antioxidants including catalase, glutathione reductase, superoxide dismutase (SOD) 1 and glutathione peroxidase was not altered by VIP except for SOD2. Furthermore, Nox1 and Nox2, major components of NADPH oxidase, were expressed in pancreatic acini, and significantly increased after H(2)O(2) treatment. Also, NADPH oxidase activity was provoked by H(2)O(2). VIP decreased NADPH oxidase activity, which was abolished by PKA inhibitor H89. These results suggested that VIP affected the mechanism of ROS production including NADPH oxidase through induction of a cAMP/PKA pathway. In conclusion, VIP reduces oxidative stress in acini through the inhibition of NADPH oxidase. These results combined with findings of our previous study suggest that VIP exerts its protective effect in pancreatic damage, not only through an inhibition of cytokine production, but also through a reduction of the injury caused by oxidative stress.

VIP-dependent increase in F508del-CFTR membrane localization is mediated by PKCε

The most common cystic fibrosis causing mutation F508del induces early degradation and reduced trafficking of cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels to the apical membrane of epithelial cells. In the human nasal epithelial cells JME/CF15, we previously reported that vasoactive intestinal peptide (VIP) exposure corrects trafficking and membrane insertion of functional F508del-CFTR channels at 37°C. Correction of trafficking was PKA dependent, whereas enhanced membrane localization involved PKC. In the present study, we have identified PKCε as the isoform involved in VIP-dependent F508del-CFTR membrane insertion. Iodide effluxes were used to monitor the presence of VIP-rescued functional F508del-CFTR channels at the surface of JME/CF15 cells maintained at 37°C. Iodide efflux peaks measured in response to stimulation with forskolin were insensitive to PKC α, β, γ, δ, ζ inhibitors. In contrast, efflux peaks were completely inhibited by pretreatment with the PKCε inhibitor peptide EAVSLKPT with an IC50 of 4.9 μM or by PKCε small interfering RNA (siRNA). Immunostaining and confocal microscopy confirmed that membrane localization of F508del-CFTR induced by VIP was abolished in the presence of EAVSLKPT but not with other isoform inhibitors. In recombinant baby hamster kidney cells, endogenously expressing PKCε but no VIP receptor, wild-type, and F508del-CFTR sensitivity to cpt-cAMP stimulation was increased by PMA treatment. Biotinylation assays and immunoblots confirmed that PMA (0.5–2 h) induced a greater than threefold increase in membrane CFTR, whereas forskolin had no effect. The PMA effect was abolished by specifically inhibiting PKCε (EAVSLKPT IC50 = 5.7 μM) but not other PKC isoforms. Taken together, these results indicate that stimulating PKCε by VIP or PMA increases membrane insertion and activity of WT- and F508del-CFTR.

Vasoactive intestinal peptide signaling axis in human leukemia

The vasoactive intestinal peptide (VIP) signaling axis constitutes a master “communication coordinator” between cells of the nervous and immune systems. To date, VIP and its two main receptors expressed in T lymphocytes, vasoactive intestinal peptide receptor (VPAC)1 and VPAC2, mediate critical cellular functions regulating adaptive immunity, including arresting CD4 T cells in G₁ of the cell cycle, protection from apoptosis and a potent chemotactic recruiter of T cells to the mucosa associated lymphoid compartment of the gastrointestinal tissues. Since the discovery of VIP in 1970, followed by the cloning of VPAC1 and VPAC2 in the early 1990s, this signaling axis has been associated with common human cancers, including leukemia. This review highlights the present day knowledge of the VIP ligand and its receptor expression profile in T cell leukemia and cell lines. Also, there will be a discussion describing how the anti-leukemic DNA binding transcription factor, Ikaros, regulates VIP receptor expression in primary human CD4 T lymphocytes and T cell lymphoblastic cell lines (e.g. Hut-78). Lastly, future goals will be mentioned that are expected to uncover the role of how the VIP signaling axis contributes to human leukemogenesis, and to establish whether the VIP receptor signature expressed by leukemic blasts can provide therapeutic and/or diagnostic information.

Effects of PACAP and VIP on hyperglycemia-induced proliferation in murine microvascular endothelial cells

Hyperglycemia is implicated both in micro- and macro-vascular complications in diabetes mellitus. Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are two known nonclassic regulators of angiogenesis, although their biological role on endothelial cell proliferation remains poorly defined. In the present study we hypothesized that either peptides might play an inhibitory role on hyperglycemia-induced cell growth. To this end, we investigated the effect of both PACAP and VIP on cell proliferation in murine microvascular endothelial cells (H5V) cultured both under euglycemic and hyperglycemic conditions (5 and 25 mM glucose, respectively) for 24, 48 h, 7 and 15 days. Results demonstrated that high glucose treatment induced a time-dependent increase in cell viability after 48 h (p<0.05), which was much more evident after 7 and 15 days (p<0.001). Similar effects were observed in cell proliferation, although significant changes were obtained after prolonged exposures to high glucose (7 and 15 days; p<0.001). The proliferative response to the glucose-enriched environment was correlated to changes in the expression of PAC1 and, to a minor extent, to VPAC2, but not VPAC1 receptors, as measured by quantitative real-time PCR. These results were further confirmed by Western blot and immunofluorescence analyses. Interestingly, 10⁻⁷ M PACAP or VIP treatment significantly attenuated hyperglycemia-induced increase in cell viability and proliferation after 7 and 15 days. Taken together, our findings demonstrate that both PACAP and VIP peptides exert an inhibitory activity on hyperglycemia-induced endothelial cell proliferation, thus suggesting that the effect might be mediated by PAC1 and VPAC2 receptors.

PACAP and VIP affect NF1 expression in rat malignant peripheral nerve sheath tumor (MPNST) cells

In our previous study we have identified PACAP, VIP and their receptors in rat malignant peripheral nerve sheath tumor (MPNST) cells, thus showing anti-apoptotic roles. Recently it has been shown that the tumor suppressor neurofibromin, encoded by the Neurofibromatosis type I (NF1) gene, promotes MPNST cells sensitivity to apoptosis after serum withdrawal. In the present study we investigated whether PACAP or VIP negatively regulate NF1 expression under normal or serum-dependent pro-apoptotic culture conditions. Results indicated that serum itself significantly influenced gene and protein levels. In fact, the low NF1 levels of cells cultured in normal serum-containing medium were remarkably increased in cells switched to low- or no-serum after 24h and 48 h. Treatment with 100 nM PACAP or VIP did not affect NF1 expression when using normal amounts of serum, whereas it significantly inhibited transcript and protein levels both in low- or no-serum cultured cells. In particular, PACAP reduced NF1 levels already after 24h in low-serum cultured cells, while VIP showed a similar effect only after serum deprivation. However, both PACAP and VIP downregulated gene and protein levels within 48 h either in low-dose and serum-starved cells. Results were confirmed by fluorescence microscopy, showing that 100 nM PACAP or VIP attenuated neurofibromin cytoplasmic localization only in low- or no-serum cultured cells. The present study provides a comprehensive analysis of both neuropeptides effect on NF1 expression in normal, low- or serum-starved MPNST cells, ameliorating the hypothesis that resistance to apoptosis in serum-deprived cells might be correlated to PACAP-/VIP-induced NF1 inhibition.

Effect of VPAC1 Blockade on Adipose Tissue Formation and Composition in Mouse Models of Nutritionally Induced Obesity

Background. The pituitary adenylate cyclase activating polypeptide (PACAP) may affect adipogenesis and adipose tissue formation through interaction with its G-protein-coupled receptor VPAC1. Methods. We have used a monoclonal antibody (MAb 23A11) blocking VPAC1 in mouse models of nutritionally induced obesity. Results. Administration of MAb 23A11 (25 mg/kg body weight i.p. twice weekly) to 5-week old male C57Bl/6 mice kept on a high-fat diet for 15 weeks had no significant effect on weight gain, nor on subcutaneous (SC) or gonadal (GON) adipose tissue mass, as compared to the control MAb 1C8. However, adipocyte hypertrophy was observed in SC adipose tissue of MAb 23A11 treated mice. In a second study, 24 weeks old obese mice were treated for 5 weeks with MAb 23A11, without effect on body weight or fat mass, as compared to treatment with MAb 1C8. In addition, MAb 23A11 had no significant effect on glucose tolerance or insulin resistance in lean or obese C57Bl/6 mice. Conclusion. Blocking VPAC1 does not significantly affect adipose tissue formation in mouse models of diet-induced obesity, although it may be associated with mild adipocyte hypertrophy.

Age-dependent association of idiopathic achalasia with vasoactive intestinal peptide receptor 1 gene

Idiopathic achalasia is a rare disorder of the oesophagus of unknown aetio-pathogenesis characterized by a myenteric inflammation, aperistalsis and insufficient lower oesophageal sphincter relaxation. Vasoactive intestinal peptide (VIP), present in the myenteric plexus, is involved in smooth muscle relaxation and acts as an anti-inflammatory cytokine. The human VIP receptor 1 gene (VIPR1) is highly polymorphic and may play a role in idiopathic achalasia. One hundred and four consecutive patients and 300 random controls from the same geographic area were typed for five SNPs mapping in the VIPR1 gene. Patients with idiopathic achalasia show a significant difference in allele, genotype and phenotype distribution of SNP rs437876 mapping in intron 4. This association, however, was almost entirely due to the group of patients with late disease onset (P = 0.0005). These results strongly suggest that idiopathic achalasia is a heterogeneous disease with a different aetiology in cases with early or late disease onset.

VPAC and PAC receptors: From ligands to function

Vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase activating polypeptides (PACAPs) share 68% identity at the amino acid level and belong to the secretin peptide family. Following the initial discovery of VIP almost four decades ago a substantial amount of knowledge has been presented describing the mechanisms of action, distribution and pleiotropic functions of these related peptides. It is now known that the physiological actions of these widely distributed peptides are produced through activation of three common G-protein coupled receptors (VPAC(1), VPAC(2) and PAC(1)R) which preferentially stimulate adenylate cyclase and increase intracellular cAMP, although stimulation of other intracellular messengers, including calcium and phospholipase D, has been reported. Using a range of in vitro and in vivo approaches, including cell-based functional assays, transgenic animals and rodent models of disease, VPAC/PAC receptor activation has been associated with numerous physiological processes (e.g. control of circadian rhythms) and clinical conditions (e.g. pulmonary hypertension), which underlies on-going research efforts and makes these peptides and their cognate receptors attractive targets for the pharmaceutical industry. However, despite the considerable interest in VPAC/PAC receptors and the processes which they mediate, there is still a paucity of selective and available, non-peptide ligands, which has hindered further advances in this field both at the basic research and clinical level. This review summarises the current knowledge of VIP/PACAP and the VPAC/PAC receptors with regard to their distribution, pharmacology, signalling pathways, splice variants and finally, the utility of animal models in exploring their physiological roles.

The role of vasoactive intestinal polypeptide and pituitary adenylate cyclase-activating polypeptide in the neural pathways controlling the lower urinary tract

Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are expressed in the neural pathways regulating the lower urinary tract. VIP-immunoreactivity (IR) is present in afferent and autonomic efferent neurons innervating the bladder and urethra, whereas PACAP-IR is present primarily in afferent neurons. Exogenously applied VIP relaxes bladder and urethral smooth muscle and excites parasympathetic neurons in bladder ganglia. PACAP relaxes bladder and urethral smooth muscle in some species (pig) but excites the smooth muscle in other species (mouse). Intrathecal administration of VIP in cats with an intact spinal cord suppresses reflex bladder activity, but intrathecal administration of VIP or PACAP in rats enhances bladder activity and suppresses urethral sphincter activity. PACAP has presynaptic facilitatory effects and direct excitatory effects on lumbosacral parasympathetic preganglionic neurons. Chronic spinal cord transection produces an expansion of VIP-IR (cats) and PACAP-IR (rats) in primary afferent axons in the lumbosacral spinal cord and unmasks spinal excitatory effects of VIP on bladder reflexes in cats. Intrathecal administration of PACAP6-38, a PAC1 receptor antagonist, reduces bladder hyperactivity in chronic spinal-cord-injured rats. These observations raise the possibility that VIP or PACAP have a role in the control of normal or abnormal voiding.

Effects of intrathecal administration of pituitary adenylate cyclase activating polypeptide on lower urinary tract functions in rats with intact or transected spinal cords

Effects of intrathecally administered pituitary adenylate cyclase activating polypeptide-38 (PACAP-38, 0.1-30 microg) on lower urinary tract function were examined in unanesthetized, decerebrate rats with an intact spinal cord and after chronic spinal cord transection (SCT). PACAP-38 was also studied in rats with intact or bilaterally transected hypogastric nerves (HGNs), to determine if sympathetic pathways to the bladder influenced responses. In SCT rats with intact HGNs under isovolumetric conditions, 30 mug of PACAP-38 but not lower doses (0.1-10 microg) increased (mean 194%) bladder contraction amplitude (BCA). In SCT rats with sectioned HGNs, 10 microg and 30 microg of PACAP-38 increased BCA by 62% and 195%, respectively. On the other hand, during continuous infusion cystometrograms (CMGs) in SCT rats with intact or sectioned HGNs, PACAP-38 (10 microg and 30 microg) markedly reduced or completely suppressed BCA (60% and 90%, respectively) and reduced external urethral sphincter (EUS) EMG activity (58% and 91%, respectively). During CMGs in spinal cord intact rats, with intact HGNs PACAP-38 30 microg increased BCA (26%) but after HGN section PACAP-38 10 microg and 30 microg increased BCA by 21% and 35%. These results suggest that after SCT, PACAP-38 activates spinal circuitry to facilitate the parasympathetic outflow to the urinary bladder and that the elimination of sympathetic pathways enhances this effect. The decrease in BCA by PACAP-38 during CMGs in SCT rats is most reasonably attributed to a reduction in urethral outlet resistance due to suppression of excitatory EUS reflexes.

PKA-dependent activation of the vascular smooth muscle isoform of KATP channels by vasoactive intestinal polypeptide and its effect on relaxation of the mesenteric resistance artery

Vasoactive intestinal polypeptide (VIP) is a potent vasodilator and has been successfully used to alleviate hypertension. Consistently, disruption of VIP gene in mice leads to hypertension. However, its downstream targets in the vascular regulation are still not well demonstrated. To test the hypothesis that the vascular smooth muscle isoform of KATP channels is a downstream target of the VIP signaling, we performed the studies on the Kir6.1/SUR2B channel expressed in HEK293 cells. We found that the channel was strongly activated by VIP. Through endogenous VIP receptors, the channel activation was reversible and dependent on VIP concentrations with the midpoint-activation concentration approximately 10 nM. The channel activation was voltage-independent and could be blocked by KATP channel blocker glibenclamide. In cell-attached patches, VIP augmented the channel open-state probability with modest suppression of the single channel conductance. The VIP-induced Kir6.1/SUR2B channel activation was blocked by PKA inhibitor RP-cAMP. Forskolin, an adenylyl cyclase activator, activated the channel similarly as VIP. The effect of VIP was further evident in the native tissues. In acutely dissociated mesenteric vascular smooth myocytes, VIP activated the KATP currents in a similar manner as in HEK293 cells. In endothelium-free mesenteric artery rings, VIP produced concentration-dependent vasorelaxation that was attenuated by glibenclamide. These results therefore indicate that the vascular isoform (Kir6.1/SUR2B) of KATP channels is a target of VIP. The channel activation relies on the PKA pathway and produces mesenteric arterial relaxation.

Effect of vasoactive intestinal peptide on gastric adenocarcinoma

BACKGROUND AND AIM

Vasoactive intestinal peptide (VIP) is a gastrointestinal hormone in the secretin-VIP family. It has been reported that VIP affects some tumor growth, and there is a VIP autocrine regulation in some cancers. However, the effect of VIP on gastric adenocarcinoma is not clear yet. The aim of the present study was to investigate the effect of VIP on gastric adenocarcinoma, especially autocrine regulation of VIP on gastric adenocarcinoma.

METHODS

VIP mRNA and protein, and its receptor mRNA (VIPR(1) and VIPR(2)) were measured in 15 normal antrum mucosa, 20 gastric adenocarcinoma tissues, and the SGC7901 gastric adenocarcinoma cell line by using reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, or radioimmunoassay methods. The effect of the VIP protein and its antagonist (D-p-Cl-Phe6, Leu17)-VIP on SGC7901 cell growth was detected by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method. The expressions of c-myc mRNA and ornithine decarboxylase (ODC) mRNA in SGC7901 cells before and after the incubated VIP protein and/or its antagonist were also measured by RT-PCR method.

RESULTS

The VIP mRNA expression in gastric adenocarcinoma tissues was significantly higher than that in normal antrum mucosa (P < 0.01). The VIP-positive immunoreactivity cells existed in 40% of gastric adenocarcinoma tissues, but not in normal tissues (P < 0.01). The VIP-positive immunoreactivity nerve fibers were observed in normal tissues, but not in adenocarcinoma tissues (P < 0.01). The expression rate of VIPR(1) mRNA in adenocarcinoma tissues was significantly lower than that in normal tissues, but that of VIPR(2) mRNA in the two kinds of tissues were similar (P > 0.05). In addition, the expression quantity of VIPR(1) mRNA and VIPR(2) mRNA in adenocarcinoma tissues was significantly lower than that in normal tissues (P < 0.05). SGC7901 cells expressed not only VIP mRNA and the VIP protein, but also VIPR(1) and VIPR(2) mRNA. 10(6) SGC7901 cells secreted 13.15 +/- 8.54 pg VIP on average. VIP did not affect the proliferation of SGC7901 cells, but the antagonist stimulated the proliferation of SGC7901 cells from 10(-5) to 10(-8) mol/L concentration incubated for 24-96 h. VIP downregulated the expressions of c-myc and ODC mRNA, but its antagonist upregulated their expressions.

CONCLUSIONS

The expression of VIP mRNA upregulates, but the expressions of VIPR mRNA downregulates in gastric adenocarcinoma tissues. The gastric adenocarcinoma tissues contain endocrine cells to secrete VIP, which show malignant specialities. The VIP autocrine regulation exists in SGC7901 cells, and potentially inhibits the proliferation of the cells by downregulating the expressions of c-myc and ODC mRNA. It suggests that VIP may play an important role in the regulation of the growth of gastric cancer cells.

Physiology and pharmacology of the human ureter: basis for current and future treatments

INTRODUCTION

This article sets out to be a review regarding agents that affect contraction and relaxation of the ureter in order to establish a basis for current and future treatments for upper urinary tract obstruction.

MATERIAL AND METHODS

A complete review of the English literature using MEDLINE was performed between 1960 and 2007 on ureter physiology and pharmacology with special emphasis on signal transduction mechanisms involved in the contractile regulation of the human ureter.

RESULTS

Activation of muscarinic and adrenergic receptors increases the amplitude of ureteral contractions. The sympathetic nerves modulate the contractions by alpha-adrenoceptors and relaxation by beta-adrenoceptors. The purinergic system is important in sensory/motor functions and ATP is an important non-adrenergic non-cholinergic (NANC) agent causing contraction. Nitric oxide (NO) is a major inhibitory NANC neurotransmitter causing relaxation. Serotonin causes contraction. Prostaglandin-F(2)alpha contracts whereas prostaglandin-E(1)/E(2) relaxes the ureter. Phosphodiesterases (PDE) and the Rho-kinase pathway have recently been identified in the human ureter. PDE-IV inhibitors, K(+) channel openers, calcium antagonists, alpha(1)-adrenoceptor antagonists and NO donors seem to be promising drugs in relieving obstruction and facilitating stone passage.

CONCLUSIONS

Further understanding of the ureteral function and pharmacology may lead to the discovery of promising new drugs that could be useful in relieving ureteral colic, facilitating spontaneous stone passage, preparing the ureter for ureteroscopy as well as acting adjunctive to extracorporeal shock-wave lithotripsy.

PACAP 38 as a modulator of immune and endocrine responses during LPS-induced acute inflammation in rats

The effect of PACAP 38 administration on neuroendocrine and immune parameters was examined in rats with LPS-induced peritonitis. Treatment with PACAP 38 alone did not influence the serum level of the cytokines and hormones examined, but significantly decreased immune cell activity. When administered together with LPS, PACAP 38 reversed its effect on immune and humoral parameters, causing a decrease in the serum concentrations of TNFalpha and corticosterone, and an increase in T4 and GH. The majority of PACAP 38 effects disappeared earlier than those previously observed for VIP. PACAP 38 appears to represent a short-lasting modulator of immune and endocrine responses during acute inflammation.

PAC1-R null isoform expression in human prostate cancer tissue

BACKGROUND

PACAP is a member of the VIP/GHRH family of neuropeptides and has important effects on prostate cell proliferation. Here we analyze the expression and localization of PACAP and its specific receptor variants (PAC(1)-R) in tissues collected from patients undergoing prostate biopsy and surgery for benign prostatic hyperplasia (BPH) and prostate cancer (PCa).

METHODS

Reverse transcriptase (RT)-polymerase chain reaction (PCR), DNA sequencing, and immunohistochemistry.

RESULTS

PACAP and PAC(1)-R were localized by immunohistochemistry in the prostate tissue. While in healthy and BPH tissues PAC(1)-R positive staining is present in all the epithelial cells lining the lumen of the acini and in some stromal cells (mostly in the apical portion of the cells), in PCa tissues, anti-PAC(1)-R antibody stained the apical portion of the cells. We provide evidence that PAC(1)-R null and SV(1)/SV(2) variants are all present in normal and hyperplastic tissues, while in PCa tissue PAC(1)-R null is the most relevant receptor variant expressed.

CONCLUSIONS

Our data demonstrates that the PAC(1)-R null variant is the most relevant isoform expressed in human PCa tissue being suggestively related with the events determining the outcome of prostate cancer.